Semiconductor memory devices are generally divided into volatile semiconductor memory devices that lose data over time, such as a dynamic random access memory (DRAM) device and a static random access memory (SRAM) device and nonvolatile semiconductor memory devices that do not lose data over time. Especially, in a volatile semiconductor memory device such as the DRAM, nowadays properties of a high storing capacity and a high response become more important as the semiconductor device is highly integrated.
Thus, researches on a material having a high permittivity instead of a conventional silicon nitride or a silicon oxide are actively under way now in order to increase an electrostatic capacity of a capacitor and improve an insulation property of a gate insulation layer. In order to acquire a material having this high permittivity, Korean Laid-Open Patent Publication No. 2004-59878 discloses a method of forming a hafnium silicon oxynitride layer by treating a hafnium oxide layer with ammonia plasma. In this method, even if the hafnium silicon oxide layer can be partially converted into hafnium silicon oxynitride layer, because the hafnium silicon oxide layer is not nitrated enough, it is not easy to secure a high dielectric constant required for the hafnium silicon oxynitride layer. Additionally, U.S. Pat. No. 6,797,645 (issued to Hwang et al.) discloses a method of using a zirconium oxide layer as a gate insulation layer after the zirconium oxide layer is nitrated by ammonia or nitrogen plasma and is oxidized again. However, even in this method, because the zirconium oxide layer is not nitrated enough, a thickness of the gate insulation layer increases and it is difficult to secure the high permittivity required.
On the other hand, it is required that a dielectric layer, which is formed between a floating gate and a control gate, should have a high permittivity in order to increase a capacity and an operation speed of a semiconductor device even in a non-volatile semiconductor device such as a flash memory device. Up to now, a dielectric layer having ONO construction in which an oxide layer, a nitride layer and an oxide layer are sequentially laminated in order has been widely used. In a non-volatile semiconductor memory device having this dielectric layer with the ONO construction, because basically a plurality of oxide layers and nitride layers are adopted as a dielectric layer, not only does the dielectric layer not have a permittivity required for the non-volatile semiconductor memory device, but a process of forming the dielectric layer is also complicated. Having considered the above problems, Korean Laid-Open Patent Publication No. 1998-32692 discloses a semiconductor device comprising a dielectric layer which is formed by doping an aluminum oxide (Al2O3), a yttrium oxide (Y2O3), a tantalum pentoxide (Ta2O5) or a vanadium pentoxide (V2O5) with zirconium (Zr), silicon (Si), titanium (Ti) and hafnium (Hf). In addition, Korean Laid-Open Patent Publication No. 1999-77767 discloses a floating gate memory device comprising a dielectric layer which includes an aluminum oxide or a yttrium oxide, or which includes an aluminum oxide, a yttrium oxide or a tantalum pentoxide doped with zirconium (Zr) or silicon (Si). When the dielectric layer including the metal oxide is adapted to the non-volatile semiconductor memory device, however, the performance of the semiconductor device drops because of a thermal damage in a successive high temperature process.